Carbon Materials as Catalyst Supports and Catalysts in the Transformation of Biomass to Fuels and Chemicals

Unseen threats in aquatic and terrestrial ecosystems: Nanoparticle persistence, transport and toxicity in natural environments

Although nanoparticles (NPs) are increasingly used in various industries, their uncontrolled environmental release presents a potential risk to water bodies, vegetation and human health. Although previous review studies evaluated the toxicity and bioaccumulation of NPs, their long-term ecological impacts and transport dynamics in aquatic and terrestrial systems remain unexplored. The current review examined the mechanistic bioaccumulation, transport and environmental persistence of NPs, highlighting the need for concurrent risk assessment, regulation and management strategies. The multifaceted nature of nanotechnology necessitates a balanced approach considering both the benefits of NPs and their potential environmental and health risks, requiring comprehensive risk assessment and management strategies. The complexities of NPs risk assessment, emphasizing the unique properties of NPs influencing their toxicity and environmental behavior are critically addressed. Strategies to mitigate NPs' environmental impact include advanced monitoring techniques, regulatory frameworks tailored to NPs' unique properties, promotion of green nanotechnology practices, and NP remediation technologies. Given the complexity and uncertainty surrounding NPs, integration of regulatory, technological, and research-based strategies is imperative. This involves detailed NPs characterization techniques providing basic data for environmental fate prediction models and understanding of biologically relevant risk assessment models to safeguard our environment and public health. In this study, the recent advances in NPs persistence, environmental transport modelling and toxicity mechanisms are uniquely integrated, providing a framework to ecological risk assessment and regulatory approaches.

Esterification of Levulinic Acid to Ethyl Levulinate over Amberlyst-15 in Flow: Systematic Kinetic Model Discrimination and Parameter Estimation

An automated reactor platform was developed using LabVIEW to conduct preplanned experiments for the identification of a kinetic model for the esterification of Levulinic acid (LA) and ethanol over heterogeneous Amberlyst-15 catalyst. A Single Pellet String Reactor of 1.25 aspect ratio was used for this kinetic study, loaded with 0.1 g of 800 μm catalyst spheres, at flow rates 20-60 μL/min, temperatures 70-100 °C, and LA feed concentrations 0.8-1.6 M. An extensive library of power law, Langmuir-Hinshelwood-Hougen-Watson and Eley-Rideal models, was screened through the application of a general procedure for model discrimination and parameter estimation. The procedure, consisting of seven steps, was applied for the investigation of different design spaces and allowed for the reformulation of models to include temperature-dependent parameters, the former leading to an increase in model identifiability and the latter resulting in enhanced model fitting. The combination of experimental data sets including the addition of the reaction product (water) in the reactor inlet stream and the incorporation of temperature dependence in the adsorption coefficients' expression led to the identification of two suitable kinetic models out of 28 candidates (a Langmuir-Hinshelwood-Hougen-Watson and an Eley-Rideal model), both of which accounted for the adsorption of water on Amberlyst-15 and fitted the experimental data satisfactorily.

Optimization of 5-HMF Synthesis by Using Catalytic Dehydration in Biphasic System with a Packed-Bed Continuous Flow Reactor

The depletion of fossil fuels and their associated environmental concerns necessitate the exploration of sustainable alternatives. 5-Hydroxymethylfurfural (5-HMF), a versatile platform chemical derived from biomass, holds significant potential for the production of biofuels, industrial intermediates, and polymers. This study employs a factorial experimental design to investigate the impact of fructose concentration, organic-to-aqueous phase ratio, and reaction time on 5-HMF yield using a biphasic system with a cation exchange resin catalyst. Optimal conditions predicted by the model, including a 100 g/L fructose solution, an organic-to-aqueous phase ratio of 8.36:1, and a reaction time of 6.91 min, were validated experimentally, resulting in a 73.45% 5-HMF yield. Subsequent purification steps, involving activated carbon adsorption for the organic phase and a two-stage extraction with butanol and NaCl for the aqueous phase, achieved 92.63% and 92.13% purity and recovery, respectively. These findings offer valuable insights for the efficient production of 5-HMF.

Recent Advances in the Design and Application of Asymmetric Carbon-Based Materials

Asymmetric carbon-based materials (ACBMs) have received significant attention in scientific research due to their unique structures and properties. Through the introduction of heterogeneous atoms and the construction of asymmetric ordered/disordered structures, ACBMs are optimized in terms of electrical conductivity, pore structure, and chemical composition and exhibit multiple properties such as hydrophilicity, hydrophobicity, optical characteristics, and magnetic behavior. Here, the recent research progress of ACBMs is reviewed, focusing on the potential of these materials for electrochemical, catalysis, and biomedical applications and their unique advantages over conventional symmetric carbon-based materials. Meanwhile, a variety of construction strategies of asymmetric structures, including template method, nanoemulsion assembly method, and self-assembly method, are described in detail. In addition, the contradictions between material synthesis and application are pointed out, such as the limitations of synthesis methods and morphology modulation means, as well as the trade-off between property improvement and production costs. Finally, the future development path of ACBMs is envisioned, emphasizing the importance of the close integration of theory and practice, and looking forward to promoting the research and development of a new generation of high-performance materials through the in-depth understanding of the design principles and action mechanisms of ACBMs.

Anchoring catalytic wet air oxidation to biomass waste management with focus on distillery stillage

Wet air oxidation is an advanced chemical reaction process involving the use of moisture and air and is applied to purposes such as to degrade existing and emerging pollutant, especially to waste types of too liquid for combustion process but too solid for biodigestion. The traditional wet air oxidation process operates on a temperature of 150-300 °C and a pressure of 0.5-20 bar whereas the supercritical oxidation applies a temperature > 374 °C and a pressure of > 2.2 bar. Wet air oxidation process technology is well matured; however, it is still a flashpoint to researchers, especially on economizing the system from applying catalysts and their supports. Wet air oxidation process catalysis is performed to improve reaction efficiency performing it at lower temperature and pressure. Such catalyzed processes are preferred based on the catalyst's selective activity and stability as well as recoverability while economizing the process energy requirement. Consequently, a catalyzed subcritical wet air oxidation is considered as an environmentally friendly and economically feasible alternative. In the past decades, plenty of studies have been done on wet air oxidation but are performed piece by piece, not comprehensively. Additionally, biologically coupled wet air oxidation of pollutants is not well revised. This paper uniquely elucidates the recent advancements in wet air oxidation and it is integral with other waste treatments to an environmentally friendly management. Structurally, this review presents the basics and state of the art of wet air oxidation, the chemical process, its catalytic and catalyst support progresses, and its application in waste and bioenergy with focus to stillage.

Biomass-derived magnetic amorphous carbon as an efficient catalyst in the conversion of fructose into 5-hydroxymethylfurfural

Fructose dehydration yields 5-hydroxymethylfurfural (5-HMF), a multifaceted precursor for clean fuels, advanced biofuels, and fuel additives. In this work, we developed a magnetic solid acid (BMSA) derived from rice husk as a proficient catalyst in the production of 5-HMF. This study investigated the influence of calcination conditions on the acid content of the catalyst, with the objective of enhancing its performance. The study factors include the effects of temperature, solvent, reaction duration, and catalyst mass, which were investigated. 5-HMF was synthesized with a yield of 72% in 3 h using 2 mg of catalyst in DMSO at 120 °C. Interestingly, the catalyst exhibited facile recovery with an external magnet and demonstrated efficient reusability for up to four cycles.

Design and engineering of microenvironments of supported catalysts toward more efficient chemical synthesis

Catalytic species such as molecular catalysts and metal catalysts are commonly attached to varieties of supports to simplify their separation and recovery and accommodate various reaction conditions. The physicochemical microenvironments surrounding catalytic species play an important role in catalytic performance, and the rational design and engineering of microenvironments can achieve more efficient chemical synthesis, leading to greener and more sustainable catalysis. In this review, we highlight recent works addressing the topic of the design and engineering of microenvironments of supported catalysts, including supported molecular catalysts and supported metal catalysts. Six types of materials, including oxide nano/microparticle, mesoporous silica nanoparticle (MSN), polymer nanomaterial, reticular material, zeolite, and carbon-based nanomaterial, are widely used as supports for the immobilization of catalytic species. We summarize and discuss the synthesis and modification of supports and the positive effects of microenvironments on catalytic properties such as metal-support interaction, molecular recognition, pseudo-solvent effect, regulating mass transfer, steric effect, etc. These design principles and engineering strategies allow access to a better understanding of structure-property relationships and advance the development of more efficient catalytic processes.

Size-Dependent Fe-Based Catalysts for the Catalytic Transfer Hydrogenation of α,β-Unsaturated Aldehydes

Metal-based catalysts ranging from nanoparticles (NPs) to the atomic level usually exhibit varying catalytic performance. The underlying size effect is both fascinating and evident. This study thoroughly investigates the size-dependent effects of Fe-based catalysts on catalytic transfer hydrogenation (CTH) of furfural (FF) at the atomic level. Fe was precisely loaded onto N-doped porous carbon in three forms: single atoms (Fe-SAs/NC), atomic clusters (Fe-ACs/NC), and nanoparticles (Fe-NPs/NC). This was achieved through meticulous control of the iron precursor composition. Remarkably, Fe-SAs/NC exhibited exceptional catalytic efficiency, achieving an FF conversion of 91.3% and a turnover frequency (TOF) of 262.3 h-1 at 110 °C, which is 9.2 times higher than Fe-ACs/NC and an impressive 93.7 times higher than Fe-NPs/NC. The high selectivity of Fe-SAs/NC toward furfuryl alcohol was further substantiated by theoretical calculations. These calculations indicated the benefits from the η1(O)-aldehyde adsorption configuration, formed by the vertical adsorption of FF molecules on the Fe-N4 active sites. Geometrical optimization of the catalyst at the atomic scale enhances its intrinsic catalytic activity and selectivity. The proposed size effect on catalytic activity provides deeper insights into the mechanism of single-atom catalytic hydrogenation and contributes to the exploration of high-performance catalysts at the atomic level.

Unlocking the catalytic potential of heterogeneous nonprecious metals for selective hydrogenation reactions

Selective hydrogenation has been employed extensively to produce value-added chemicals and fuels, greatly alleviating the problems of fossil resources and green synthesis. However, the design and synthesis of highly efficient catalysts, especially those that are inexpensive and abundant in the earth's crust, is still required for basic research and subsequent industrial applications. In recent years, many studies have revealed that the rational design and synthesis of heterogeneous catalysts can efficaciously improve the catalytic performance of hydrogenation reactions. However, the relationship between nonprecious metal catalysts and hydrogenation performance from the perspective of different catalytic systems still remains to be understood. In this review, we provide a comprehensive and systematic overview of the recent advances in the synthesis of nonprecious metal catalysts for heterogeneous selective hydrogenation reactions including thermocatalytic hydrogenation/transfer hydrogenation, photocatalytic hydrogenation and electrocatalytic reduction. In addition, we also aim to provide a clear picture of the recent design strategies and proposals for the nonprecious metal catalysed hydrogenation reactions. Finally, we discuss the current challenges and future research opportunities for the precise design and synthesis of nonprecious metal catalysts for selective hydrogenation reactions.

In Situ Construction of Perovskite Pr0.5Ba0.5Mn0.8Co0.1Ru0.1O2.5+δ/CoRu Nanoparticles with Co-N-C Composite Enabling Efficient Bifunctional Electrocatalyst for Zinc-Air Batteries

Bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential components of rechargeable zinc-air batteries. In this study, we synthesized a Pr0.5Ba0.5Mn0.8Co0.1Ru0.1O2.5+δ (PBMCRO) perovskite composite with in situ exsolved CoRu nanoparticles and Co-N-C, functioning as an efficient bifunctional electrocatalyst for zinc-air batteries. The in situ exsolution of CoRu nanoparticles from the perovskite oxide was facilitated by the reducing action of 2-methylimidazole (2-MIM). Concurrently, Co-N-C was used to decorate PBMCRO, forming a novel bifunctional composite electrode of Co-N-C-PBMCRO. The incorporation of CoRu nanoparticles introduces a significant number of electrochemically active oxygen vacancies in the perovskite matrix, enhancing ORR and OER performance. Additionally, the Co-N-C synergistically improves electrochemical activity while preserving the structural stability of the perovskite oxide. The prepared Co-N-C-PBMCRO catalyst demonstrates significantly enhanced bifunctional performance compared to the undecorated pristine perovskite Pr0.5Ba0.5MnO3-δ (PBMO). The zinc-air battery with Co-N-C-PBMCRO catalyst achieve a peak power density of approximately 90 mW/cm2 and exhibit remarkable cycling stability for 788 h. This study presents a novel and effective strategy to enhance the catalytic performance of perovskite-based air electrodes for rechargeable metal-air batteries.

Catalytic degradation of organic pollutants in aqueous systems: A comprehensive review of peroxyacetic acid-based advanced oxidation processes

Peroxyacetic acid (PAA)-based advanced oxidation processes (AOPs) have emerged as a promising treatment method to decontaminate organic pollutants. This review thoroughly evaluated the use of PAA-based AOPs, including their synthesis techniques, physicochemical features, and reaction pathways with pollutants. It also illustrated two primary channels: free radical pathways and non-radical pathways during the PAA activation processes and introduced various methods for activating PAA, including energy radiation, transition metal catalysis, and carbon catalysis. Additionally, this review comprehensively presented the advancements in research on PAA-based AOPs for wastewater treatment. Furthermore, the influences of key parameters on system performance, such as pH, catalyst loading, PAA dosage, and interfering species, were summarized. By critically evaluating mechanisms, performance, and prospects, this review served as a valuable resource for researchers and practitioners involved in the development and implementation of PAA-based AOPs for sustainable water remediation.

Efficient synthesis of α-aminophosphonates using magnetically retrievable ionic nanocatalysts under ultrasound acceleration

Magnetic supported ionic liquids are a unique subclass of ionic liquids that possess the ability to respond to external magnetic fields, combining the advantageous properties of traditional ILs with this magnetic responsiveness. A novel magnetic ionic nanocatalyst of Fe3O4@SiO2@CPTMS-DTPA was prepared by anchoring an ionic liquid, CPTMS-DTPA, onto the surface of silica-modified Fe3O4. The morphology, chemical structure and magnetic property of the magnetic ionic nanocatalyst structure was characterized using scanning electron microscopy, X-ray powder diffraction, Fourier transformation infrared spectroscopy, vibrating sample magnetometer, and thermogravimetric analysis. The results confirmed the successful attachment of the ionic liquid to the magnetic substrate. Subsequently, the magnetic nanocatalyst was employed for the green synthesis of α-aminophosphonate derivatives. The synthesis was achieved via a one-pot, three-component reaction involving various aldehydes, amines, and different trialkyl(aryl) phosphite derivatives. The reactions were conducted under ultrasound conditions for a duration of 10-25 min, resulting in good to excellent product yields (64-97%). Its recyclability was tested for up to five cycles using magnetic separation which makes it a highly efficient method for quickly separating catalysts from the reaction medium without compromising catalytic activity.

Biochar Meets Single-Atom: A Catalyst for Efficient Utilization in Environmental Protection Applications and Energy Conversion

Single-atom catalysts (SACs), combining the advantages of multiphase and homogeneous catalysis, have been increasingly investigated in various catalytic applications. Carbon-based SACs have attracted much attention due to their large specific surface area, high porosity, particular electronic structure, and excellent stability. As a cheap and readily available carbon material, biochar has begun to be used as an alternative to carbon nanotubes, graphene, and other such expensive carbon matrices to prepare SACs. However, a review of biochar-based SACs for environmental pollutant removal and energy conversion and storage is lacking. This review focuses on strategies for synthesizing biochar-based SACs, such as pre-treatment of organisms with metal salts, insertion of metal elements into biochar, or pyrolysis of metal-rich biomass, which are more simplistic ways of synthesizing SACs. Meanwhile, this paper attempts to 1) demonstrate their applications in environmental remediation based on advanced oxidation technology and energy conversion and storage based on electrocatalysis; 2) reveal the catalytic oxidation mechanism in different catalytic systems; 3) discuss the stability of biochar-based SACs; and 4) present the future developments and challenges regarding biochar-based SACs.

Supporting Nano Catalysts for the Selective Hydrogenation of Biomass-derived Compounds

The selective hydrogenation of biomass derivatives presents a promising pathway for the production of high-value chemicals and fuels, thereby reducing reliance on traditional petrochemical industries. Recent strides in catalyst nanostructure engineering, achieved through tailored support properties, have significantly enhanced the hydrogenation performance in biomass upgrading. A comprehensive understanding of biomass selective upgrading reactions and the current advancement in supported catalysts is crucial for guiding future processes in renewable biomass. This review aims to summarize the development of supported nanocatalysts for the selective hydrogenation of the US DOE's biomass platform compounds derivatives into valuable upgraded molecules. The discussion includes an exploration of the reaction mechanisms and conditions in catalytic transfer hydrogenation (CTH) and high-pressure hydrogenation. By thoroughly examining the tailoring of supports, such as metal oxide catalysts and porous materials, in nano-supported catalysts, we elucidate the promoting role of nanostructure engineering in biomass hydrogenation. This endeavor seeks to establish a robust theoretical foundation for the fabrication of highly efficient catalysts. Furthermore, the review proposes prospects in the field of biomass utilization and address application bottlenecks and industrial challenges associated with the large-scale utilization of biomass.

Synergistic augmentation and fundamental mechanistic exploration of β-Ga2O3-rGO photocatalyst for efficient CO2 reduction

We explore the novel photodecomposition capabilities of β-Ga2O3 when augmented with reduced graphene oxide (rGO). Employing real-time spectroscopy, this study unveils the sophisticated mechanisms of photodecomposition, identifying an optimal 1 wt% β-Ga2O3-rGO ratio that substantially elevates the degradation efficiency of Methylene Blue (MB). Our findings illuminate a direct relationship between the photocatalyst's composition and its performance, with the quantity of rGO synthesis notably influencing the catalyst's morphology and consequently, its photodegradation potency. The 1 wt% β-Ga2O3-rGO composition stands out in its class, showing a notable 4.7-fold increase in CO production over pristine β-Ga2O3 and achieving CO selectivity above 98%. This remarkable performance is a testament to the significant improvements rendered by our novel rGO integration technique. Such promising results highlight the potential of our custom-designed β-Ga2O3-rGO photocatalyst for critical environmental applications, representing a substantial leap forward in photocatalytic technology.

Machine learning screening of biomass precursors to prepare biomass carbon for organic wastewater purification: A review

In the past decades, the amount of biomass waste has continuously increased in human living environments, and it has attracted more and more attention. Biomass is regarded as the most high-quality and cost-effective precursor material for the preparation carbon of adsorbents and catalysts. The application of biomass carbon has extensively explored. The efficient application of biomass carbon in organic wastewater purification were reviewed. With briefly introducing biomass types, the latest progress of Machine learning in guiding the preparation and application of biomass carbon was emphasized. The key factors in constructing efficient biomass carbon for adsorption and catalytic applications were discussed. Based on the functional groups, rich pore structure and active site of biomass carbon, it exhibits high efficiency in water purification performance in the fields of adsorption and catalysis. In addition, out of a firm belief in the enormous potential of biomass carbon, the remaining challenges and future research directions were discussed.

Activity and product distribution in Ni-Co and Ni-Cu catalyst-mediated lignin depolymerization into phenolic substances with isopropanol H-donating solvent

Lignin, a vital renewable biopolymer, serves as the Earth's primary source of aromatics and carbon. Its depolymerization presents significant potential for producing phenolic fine chemicals. This study assesses promoted Ni-based bimetallic catalysts (Ni-Co/C and Ni-Cu/C) supported on activated carbon in isopropanol for lignin depolymerization, compared to monometallic counterparts. BET, SEM, EDX, and XPS analyses highlight their physicochemical properties and promotional effects, enhancing hydrogenolysis activity and hydrogen transformation. Reaction parameter exploration elucidates the influence on lignin depolymerization, with cobalt and copper as promoters notably increasing conversion and monomer yield. Ni-Co/C exhibits the highest lignin conversion (94.2%) and maximum monomer yield (53.1 wt%) under specified conditions, with lower activation energy (36.1 kJ/mol) and higher turnover frequency (31.6 h-1) compared to Ni/C. FT-IR, GPC, GC-FID, and GC-MS analyses confirm effective depolymerization, identifying 20 monomer products. Proposed reaction mechanisms underscore the potential of Ni-based bimetallic catalysts for lignin valorization, offering insights into developing efficient catalytic systems for lignin hydrogenolysis. This research enhances understanding and facilitates the development of selective catalytic processes for lignin valorization.

Selective production of high-value fuel via catalytic upgrading of bio-oil over nitrogen-doped carbon-alumina hybrid supported cobalt catalysts

Bio-oil derived from biomass fast pyrolysis can be upgraded to gasoline and diesel alternatives by catalytic hydrodeoxygenation (HDO). Here, the novel nitrogen-doped carbon-alumina hybrid supported cobalt (Co/NCAn, n = 1, 2.5, 5) catalyst is established by a coagulation bath technique. The optimized Co/NCA2.5 catalyst presented 100 % conversion of guaiacol, high selectivity to cyclohexane (93.6 %), and extremely high deoxygenation degree (97.3 %), respectively. Therein, the formation of cyclohexanol was facilitated by stronger binding energy and greater charge transfer between Co and NC which was unraveled by density functional theory calculations. In addition, the appropriate amount of Lewis acid sites enhanced the cleavage of the C-O bond in cyclohexanol, finally resulting in a remarkable selectivity for cyclohexane. Finally, the Co/NCA2.5 catalyst also exhibited excellent selectivity (93.1 %) for high heating value hydrocarbon fuel in crude bio-oil HDO. This work provides a theoretical basis on N dopants collaborating alumina hybrid catalysts for efficient HDO reaction.

Determining the orderliness of carbon materials with nanoparticle imaging and explainable machine learning

Carbon materials have paramount importance in various fields of materials science, from electronic devices to industrial catalysts. The properties of these materials are strongly related to the distribution of defects-irregularities in electron density on their surfaces. Different materials have various distributions and quantities of these defects, which can be imaged using a procedure that involves depositing palladium nanoparticles. The resulting scanning electron microscopy (SEM) images can be characterized by a key descriptor-the ordering of nanoparticle positions. This work presents a highly interpretable machine learning approach for distinguishing between materials with ordered and disordered arrangements of defects marked by nanoparticle attachment. The influence of the degree of ordering was experimentally evaluated on the example of catalysis via chemical reactions involving carbon-carbon bond formation. This represents an important step toward automated analysis of SEM images in materials science.

Sustainable carbonaceous nanomaterial supported palladium as an efficient ligand-free heterogeneouscatalyst for Suzuki-Miyaura coupling

A novel ligand-free heterogeneous catalyst was synthesized via pyrolysis of Samanea saman pods to produce carbon nanospheres (SS-CNSs), which served as a carbon support for immobilizing palladium nanoparticles through an in situ reduction technique (Pd/SS-CNS). The SS-CNSs effectively integrated 3% of Pd on their surfaces with no additional activation procedures needed. The nanomaterials obtained underwent thorough characterization employing various techniques such as FT-IR, XRD, FE-SEM, TEM, EDS, ICP-AES, and BET. Subsequently, the efficiency of this Pd/SS-CNS catalyst was assessed for the synthesis of biaryl derivatives via Suzuki coupling, wherein different boronic acids were coupled with various aryl halides using an environmentally benign solvent mixture of EtOH/H2O and employing only 0.1 mol% of Pd/SS-CNS. The catalytic system was conveniently recovered through centrifugation and demonstrated reusability without any noticeable decline in catalytic activity. This approach offers economic viability, ecological compatibility, scalability, and has the potential to serve as an alternative to homogeneous catalysis.

Captopril supported on magnetic graphene nitride, a sustainable and green catalyst for one-pot multicomponent synthesis of 2-amino-4H-chromene and 1,2,3,6-tetrahydropyrimidine

Captopril (CAP) is a safe, cost-effective, and environmentally organic compound that can be used as an effective organo-catalyst. Functional groups of captopril make it capable to attach to solid support and acting as promoters in organic transformations. In this work, captopril was attached to the surface of magnetic graphene nitride by employing a linker agent. The synthesized composite efficiently catalyzed two multicomponent reactions including the synthesis of 1,2,3,6-tetrahydropyrimidine and 2-amino-4H-chromene derivatives. A large library of functional targeted products was synthesized in mild reaction conditions. More importantly, this catalyst was stable and magnetically recycled and reused for at least five runs without losing catalytic activity.

Carbon Nanotube-Supported Bimetallic Core-Shell (M@Pd/CNT (M: Zn, Mn, Ag, Co, V, Ni)) Cathode Catalysts for H2O2 Fuel Cells

M@Pd/CNT (M: Zn, Mn, Ag, Co, V, Ni) core-shell and Pd/CNT nanoparticles were prepared by sodium borohydride reduction and explored as cathode catalysts for the hydrogen peroxide reduction reaction. Electrochemical and physical characterization techniques are applied to explore the characteristics of the produced electrocatalysts. The cyclic voltammetry (CV) experiments show that Zn@Pd/CNT-modified electrodes have a current density of 273.2 mA cm-2, which is 3.95 times higher than that of Pd/CNT. According to the chronoamperometric curves, Zn@Pd/CNT has the highest steady-state current density for the H2O2 electro-reduction process among the synthesized electrocatalysts. Moreover, electrochemical impedance spectroscopy (EIS) spectra confirmed the previous electrochemical results due to the lowest charge transfer resistance (35 Ω) with respect to other electrocatalysts.

Ionothermal synthesis of magnetic N-doped porous carbon to immobilize Pd nanoparticles as an efficient nanocatalyst for the reduction of nitroaromatic compounds

Carbon materials play important roles as catalysts or catalyst supports for reduction reactions owing to their high porosity, large specific surface area, great electron conductivity, and excellent chemical stability. In this paper, a mesoporous N-doped carbon substrate (exhibited as N-C) has been synthesized by ionothermal carbonization of glucose in the presence of histidine. The N-C substrate was modified by Fe3O4 nanoparticles (N-C/Fe3O4), and then Pd nanoparticles were stabilized on the magnetic substrate to synthesize an eco-friendly Pd catalyst with high efficiency, magnetic, reusability, recoverability, and great stability. To characterize the Pd/Fe3O4-N-C nanocatalyst, different microscopic and spectroscopic methods such as FT-IR, XRD, SEM/EDX, and TEM were applied. Moreover, Pd/Fe3O4-N-C showed high catalytic activity in reducing nitroaromatic compounds in water at ambient temperatures when NaBH4 was used as a reducing agent. The provided nanocatalyst's great catalytic durability and power can be attributed to the synergetic interaction among well-dispersed Pd nanoparticles and N-doped carbonaceous support.

Recent advancements and challenges in emerging applications of biochar-based catalysts

The sustainable utilization of biochar produced from biomass waste could substantially promote the development of carbon neutrality and a circular economy. Due to their cost-effectiveness, multiple functionalities, tailorable porous structure, and thermal stability, biochar-based catalysts play a vital role in sustainable biorefineries and environmental protection, contributing to a positive, planet-level impact. This review provides an overview of emerging synthesis routes for multifunctional biochar-based catalysts. It discusses recent advances in biorefinery and pollutant degradation in air, soil, and water, providing deeper and more comprehensive information of the catalysts, such as physicochemical properties and surface chemistry. The catalytic performance and deactivation mechanisms under different catalytic systems were critically reviewed, providing new insights into developing efficient and practical biochar-based catalysts for large-scale use in various applications. Machine learning (ML)-based predictions and inverse design have addressed the innovation of biochar-based catalysts with high-performance applications, as ML efficiently predicts the properties and performance of biochar, interprets the underlying mechanisms and complicated relationships, and guides biochar synthesis. Finally, environmental benefit and economic feasibility assessments are proposed for science-based guidelines for industries and policymakers. With concerted effort, upgrading biomass waste into high-performance catalysts for biorefinery and environmental protection could reduce environmental pollution, increase energy safety, and achieve sustainable biomass management, all of which are beneficial for attaining several of the United Nations Sustainable Development Goals (UN SDGs) and Environmental, Social and Governance (ESG).

A Green Approach to Obtaining Glycerol Carbonate by Urea Glycerolysis Using Carbon-Supported Metal Oxide Catalysts

The results of sustainable and selective synthesis of glycerol carbonate (GC) from urea and glycerol under ambient pressure using carbon-fiber-supported metal oxide catalysts are reported. Carbon fibers (CF) were prepared via a catalytic chemical vapor deposition method (CCVD) using Ni as a catalyst and liquefied petroleum gas (LPG) as a cheap carbon source. Supported metal oxide catalysts were obtained by an incipient wetness impregnation technique using Zn, Ba, Cr, and Mg nitrates. Finally, the samples were pyrolyzed and oxidized in an air flow. The obtained catalysts (10%MexOy/CFox) were tested in the reaction of urea glycerolysis at 140 °C for 6 h under atmospheric pressure, using an equimolar ratio of reagents and an inert gas flow for NH3 removal. Under the applied conditions, all of the prepared catalysts increased the glycerol conversion and glycerol carbonate yield compared to the blank test, and the best catalytic performance was shown by the CFox-supported ZnO and MgO systems. Screening of the reaction conditions was carried out by applying ZnO/CFox as a catalyst and considering the effect of reaction temperature, molar ratio of reagents, and the mode of the inert gas flow through the reactor on the catalytic process. Finally, a maximum yield of GC of about 40%, together with a selectivity to glycerol carbonate of ~100%, was obtained within 6 h of reaction at 140 °C using a glycerol-to-urea molar ratio of 1:1 while flowing Ar through the reaction mixture. Furthermore, a positive heterogeneous catalytic effect of the CFox support on the process was noticed.

Cellulose based biopolymer nanoscaffold: A possible biomedical applications

In this work, a combination of cellulose nanofiber (CNF), coffee beans powder (CBP), and reduced graphene oxide (rGO) are used to design a nanowound dressing sheet (Nano-WDS), by vacuum pressure, for their sustained application in wound healing. Nano-WDS was analysed for its mechanical, antimicrobial, biocompatibility, etc., The Nano-WDS had favourable results of the tensile strength (12.85 ± 0.10 MPa), elongation at break (09.45 ± 0.28 %), water absorption (31.14 ± 0.04 %), and thickness (00.76 ± 0.02 mm). The biocompatibility study of Nano-WDS was analysed using human keratinocyte cell line (HaCaT), which showed excellent cell growth. The antibacterial activity was reflected in the Nano-WDS against the E.coli and S.aureus bacteria. Cellulose comprises the glucose unit and reduced graphene oxides are combined to create macromolecular interaction. The surface activity of cellulose-formed nanowound dressing sheet demonstrates a wound tissue engineering application. Based on the result of the study was proved suitable for bioactive wound dressing applications. The research proves that these Nano-WDS could be successfully used for the production of wound healing materials.

Preparation and Testing of a Palladium-Decorated Nitrogen-Doped Carbon Foam Catalyst for the Hydrogenation of Benzophenone

Catalytic activity of a palladium catalyst with a porous carbon support was prepared and tested for benzophenone hydrogenation. The selectivity and yields toward the two possible reaction products (benzhydrol and diphenylmethane) can be directed by the applied solvent. It was found that in isopropanol, the prepared support was selective towards diphenylmethane with high conversion (99% selectivity and 99% benzophenone conversion on 323 K after 240 min). This selectivity might be explained by the presence of the incorporated structural nitrogens in the support.

Potential of agro-industrial residues from the Amazon region to produce activated carbon

Thousands of tons of residual lignocellulosic biomass are produced and discarded by agroindustries in the Amazon. These biomasses could be harnessed and used in the preparation of activated carbon, in view of the growing demand for this product with high added value, however, little is known about their characteristics, in addition to their potential as precursors of activated carbon. Therefore, the aim of this work was to evaluate the potential of four different biomasses in the preparation and quality of activated carbon. Residues from the processing of the fruits of acai, babassu, Brazil nut, and oil palm were collected, characterized, carbonized, physically activated with CO₂, and characterized. The contents of the total extractives, insoluble lignin, minerals, holocellulose, and elemental (CHNS-O) were analyzed. The surface area and surface morphology were determined from the AC produced, and adsorption tests for methylene blue and phenol were performed. The four biomasses showed potential for use in the preparation of CA; the residues presented high contents of lignin (21.83-55.76%) and carbon (46.49-53.79%). AC were predominantly microporous, although small mesopores could be observed. The AC had a surface area of 569.65-1101.26 m² g^-1, a high methylene blue (93-390 mg g^-1), and phenol (159-595 mg g^-1) adsorption capacities. Babassu-AC stood out compared to the AC of the other analyzed biomasses, reaching the best results.

A review on nanoparticles: characteristics, synthesis, applications, and challenges

The significance of nanoparticles (NPs) in technological advancements is due to their adaptable characteristics and enhanced performance over their parent material. They are frequently synthesized by reducing metal ions into uncharged nanoparticles using hazardous reducing agents. However, there have been several initiatives in recent years to create green technology that uses natural resources instead of dangerous chemicals to produce nanoparticles. In green synthesis, biological methods are used for the synthesis of NPs because biological methods are eco-friendly, clean, safe, cost-effective, uncomplicated, and highly productive. Numerous biological organisms, such as bacteria, actinomycetes, fungi, algae, yeast, and plants, are used for the green synthesis of NPs. Additionally, this paper will discuss nanoparticles, including their types, traits, synthesis methods, applications, and prospects.

Production of Alkyl Levulinates from Carbohydrate-Derived Chemical Intermediates Using Phosphotungstic Acid Supported on Humin-Derived Activated Carbon (PTA/HAC) as a Recyclable Heterogeneous Acid Catalyst

This work reports a straightforward and high-yielding synthesis of alkyl levulinates (ALs), a class of promising biofuel, renewable solvent, and chemical feedstock of renewable origin. ALs were prepared by the acid-catalyzed esterification of levulinic acid (LA) and by the alcoholysis of carbohydrate-derived chemical platforms, such as furfuryl alcohol (FAL) and α-angelica lactone (α-AGL). Phosphotungstic acid (PTA) was chosen as the solid acid catalyst for the transformation, which was heterogenized on humin-derived activated carbon (HAC) for superior recyclability. Using HAC as catalyst support expands the scope of valorizing humin, a complex furanic resin produced inevitably as a side product (often considered waste) during the acid-catalyzed hydrolysis/dehydration of sugars and polymeric carbohydrates. Under optimized conditions (150 °C, 7 h, 25 wt.% of 20%PTA/HAC-600 catalyst), ethyl levulinate (EL) was obtained in an 85% isolated yield starting from FAL. Using the general synthetic protocol, EL was isolated in 88% and 84% yields from LA and α-AGL, respectively. The 20%PTA/HAC-600 catalyst was successfully recovered from the reaction mixture and recycled for five cycles. A marginal loss in the yield of ALs was observed in consecutive catalytic cycles due to partial leaching of PTA from the HAC support.

Plant-Biomass-Derived Carbon Materials as Catalyst Support, A Brief Review

Carbon materials are widely used in catalysis as effective catalyst supports. Carbon supports can be produced from coal, organic precursors, biomass, and polymer wastes. Biomass is one of the promising sources used to produce carbon-based materials with a high surface area and a hierarchical structure. In this review, we briefly discuss the methods of biomass-derived carbon supported catalyst preparation and their application in biodiesel production, organic synthesis reactions, and electrocatalysis.

Review of Advances in the Utilization of Biochar-Derived Catalysts for Biodiesel Production

Biochar, obtained from the thermal decomposition of different biomass sources, can be used in various scientific technologies by virtue of its distinguishing performance. Recent developments in advanced biochar synthesis methods have led to continuous growth in the literature related to bulk biochar products and synthesized biochar substrates. This review specifically summarizes the current advanced methods for the synthesis of functional biochar catalysts and applications in (trans)esterification. Herein, first the method and design of synthesized biochar substrate catalysts are briefly introduced. Second, the applications of these synthesized biochar substrate catalysts upon (trans)esterification are comprehensively discussed. Finally, the current research status and the future perspectives of the synthesized biochar substrate catalyst are presented. It is expected that this summary will provide perspectives and instructions for future work on synthesized biochar catalysts for biodiesel products.

An Atomistic View of Platinum Cluster Growth on Pristine and Defective Graphene Supports

Density functional theory (DFT) is used to systematically investigate the electronic structure of platinum clusters grown on different graphene substrates. Platinum clusters with 1 to 10 atoms and graphene vacancy defect supports with 0 to 5 missing C atoms are investigated. Calculations show that Pt clusters bind more strongly as the vacancy size increases. For a given defect size, increasing the cluster size leads to more endothermic energy of formation, suggesting a templating effect that limits cluster growth. The opposite trend is observed for defect-free graphene where the formation energy becomes more exothermic with increasing cluster size. Calculations show that oxidation of the defect weakens binding of the Pt cluster, hence it is suggested that oxygen-free graphene supports are critical for successful attachment of Pt to carbon-based substrates. However, once the combined material is formed, oxygen adsorption is more favorable on the cluster than on the support, indicating resistance to oxidative support degradation. Finally, while highly-symmetric defects are found to encourage formation of symmetric Pt clusters, calculations also reveal that cluster stability in this size range mostly depends on the number of and ratio between PtC, PtPt, and PtO bonds; the actual cluster geometry seems secondary.

Catalytic advancements in carbonaceous materials for bio-energy generation in microbial fuel cells: a review

Microbial fuel cells (MFCs) are a sustainable alternative for wastewater treatment and clean energy generation. The efficiency of the technology is dependent on the cathodic oxygen reduction reaction, where the sluggish reaction kinetics hampers its propensity. Carbonaceous materials with high electrical conductivity have been widely explored for oxygen reduction reaction (ORR) catalysts. Here, incorporating transition metal (TM) and heteroatom into carbon could further enhance the ORR activity and power generation in MFCs. Nitrogen (N)-doped carbons have also been a popular research hotspot due to abundant active sites formed, resulting in superior conductivity, stability, and catalytic activity over carbons. This review summarizes the progress in the carbon-based materials (primary focus on the cathode) for ORR and their utilization in MFCs. Furthermore, we discussed the conceptualization of MFCs and carbonaceous materials to instigate the ORR kinetics and power generation in MFC. Furthermore, prospects of carbon-based materials for actual application in bio-energy generation have been discussed. Carbonaceous catalysts and biomass-derived carbons exhibit good potential to replace precious Pt catalysts for ORR. M-N-C catalysts were found to be the most suitable catalysts. Electrocatalysts with MN_x sites are able to achieve excellent activity and high-power output by taking advantage of the active site exposure and rapid mass transfer rate. Moreover, the use of biomass-derived carbons/self-doped carbons could further reduce the overall cost of catalysts. It is anticipated that the research gaps and future perspectives discussed will show new avenues to develop excellent electrocatalysts for better performance and transformation of technology to industrial applications.

Structure–activity relationships of LDH catalysts for the glucose-to-fructose isomerisation in ethanol

Hydrotalcite catalysed liquid phase glucose isomerisation in EtOH.

Preparation of Nitrogen Doped Biochar-Based Iron Catalyst for Enhancing Gasoline-Range Hydrocarbons Production

Developing catalysts to obtain high space time yield (STY) of gasoline-range hydrocarbons via Fischer-Tropsch synthesis (FTS) is a huge challenge due to the restriction of Anderson-Schulz-Flory distribution. Herein, a nitrogen doped biochar-based iron catalyst was synthesized by a one-step method using sugar cane bagasse as carbon precursor, which exhibited an excellent gasoline STY of 8.65 g_C5-12 g_Fe^-1 h^-1, exceeding most reported catalysts. A strong positive relationship between the amount of pyrrolic N and long-chain hydrocarbons selectivity was displayed. The characterization results indicated that pyrrolic N configuration on anchor sites tuned effectively the dispersion of iron species and metal-support interaction as well as CO adsorption, improving the FTS performance.

Recent Advances in Carbon-Based Iron Catalysts for Organic Synthesis

Carbon-based iron catalysts combining the advantages of iron and carbon material are efficient and sustainable catalysts for green organic synthesis. The present review summarizes the recent examples of carbon-based iron catalysts for organic reactions, including reduction, oxidation, tandem and other reactions. In addition, the introduction strategies of iron into carbon materials and the structure and activity relationship (SAR) between these catalysts and organic reactions are also highlighted. Moreover, the challenges and opportunities of organic synthesis over carbon-based iron catalysts have also been addressed. This review will stimulate more systematic and in-depth investigations on carbon-based iron catalysts for exploring sustainable organic chemistry.